if_msk.c patch for yukon ec hanging

[Karim Fodil-Lemelin]

Hello,

I'd like to summit a patch that fixes a hanging issue related to Rx FIFO 
overrun on the following chips and rev (tested):

ID:
CHIP_ID_YUKON_EC

REV:
CHIP_REV_YU_EC_A2
CHIP_REV_YU_EC_A3

(I haven't tested it on CHIP_REV_YU_EC_A1)

@@ -3813,16 +3805,24 @@
                     GMR_FS_ANY_ERR);
         }

-       /*
-        * Set Rx FIFO flush threshold to 64 bytes + 1 FIFO word
-        * due to hardware hang on receipt of pause frames.
-        */
-       reg = RX_GMF_FL_THR_DEF + 1;
-       /* Another magic for Yukon FE+ - From Linux. */
-       if (sc->msk_hw_id == CHIP_ID_YUKON_FE_P &&
-           sc->msk_hw_rev == CHIP_REV_YU_FE_P_A0)
-               reg = 0x178;
-       CSR_WRITE_2(sc, MR_ADDR(sc_if->msk_port, RX_GMF_FL_THR), reg);
+       if (sc->msk_hw_id == CHIP_ID_YUKON_EC){
+         /* Set Rx FIFO flush threshold to 64 bytes. */
+         CSR_WRITE_4(sc, MR_ADDR(sc_if->msk_port, RX_GMF_FL_THR),
+                     RX_GMF_FL_THR_DEF);
+       }
+       else {
+         /*
+          * Set Rx FIFO flush threshold to 64 bytes + 1 FIFO word
+          * due to hardware hang on receipt of pause frames.
+          */
+         reg = RX_GMF_FL_THR_DEF + 1;
+         /* Another magic for Yukon FE+ - From Linux. */
+         if (sc->msk_hw_id == CHIP_ID_YUKON_FE_P &&
+             sc->msk_hw_rev == CHIP_REV_YU_FE_P_A0)
+           reg = 0x178;
+         CSR_WRITE_2(sc, MR_ADDR(sc_if->msk_port, RX_GMF_FL_THR), reg);
+       }

         /* Configure Tx MAC FIFO. */
         CSR_WRITE_4(sc, MR_ADDR(sc_if->msk_port, TX_GMF_CTRL_T), 
GMF_RST_SET);

The symptoms of the problem was that if a large amount of small TCP 
packets were fired up at the interface it would generate an interrupt 
from MAC1 with a GMAC status of 0x7 and while the chip Tx would still 
function the Rx would 'hang'. Triggering a watchdog timeout would make 
it work again sometimes but calling mskc_reset() didn't worked at all. 
It turned out that we had an old driver written by Pyun YongHyeon that 
would work flawlessly on that chip. This patch helps support that old chip.

I hope this helps someone,

Karim.

PS: The patch line numbers are against 'CURRENT' r214406 but should also 
apply to FBSD 7 and 8.